Yarn feed roller assembly

ABSTRACT

A yarn feed roller assembly for a tufting machine pattern attachment including a plurality of hollow drive shafts each having a plurality of feed rolls rotatably mounted thereon. An electromagnetic clutch having a rotating field keyed on the shaft within each feed roll selectively transmits the rotation of the shaft to the roll. Corresponding rolls of the drive shafts are drivingly connected one to the other. Between each pair of rolls is positioned a stationary yarn holding gear having teeth on only a portion thereof which bind with a corresponding gear on the other drive shafts and have yarn receiving grooves for surplus yarn when tufting with less yarn ends than the machine is capable of using. Slip rings located in a group at one end of each shaft receive electrical leads which pass through the shaft center from the clutch field coil. A horse shoe shaped brush retainer rides on each slip ring and is prevented from rotating by a quick release hook member which fits over a securing bar and is held in place by a spring member that also supplies the electrical power to the brushes.

United States Patent [191 Lear et al.

[451 Dec. 16, 1975 YARN FEED ROLLER ASSEMBLY [75] Inventors: Edward C. Lear, Farleton; Nigel S.

Fitton, Great l-larwood, both of England [73] Assignee: The Singer Company, New York,

[22] Filed: Oct. 17, 1974 [21] Appl. No.: 515,769

[30] Foreign Application Priority Data Primary Examiner-H. Hampton Hunter Attorney, Agent, or Firm-Edward L. Bell; Robert E. Smith; Alan Ruderman [57] ABSTRACT A yarn feed roller assembly for a tufting machine pattern attachment including a plurality of hollow drive shafts each having a plurality of feed rolls rotatably mounted thereon. An electromagnetic clutch having a rotating field keyed on the shaft within each feed roll selectively transmits the rotation of the shaft to the roll. Corresponding rolls of the drive shafts are drivingly connected one to the other. Between each pair of rolls is positioned a stationary yarn holding gear having teeth on only a portion thereof which bind with a corresponding gear on the other drive shafts and have yarn receiving grooves for surplus yarn when tufting with less yarn ends than the machine is capable of using. Slip rings located in a group at one end of each shaft receive electrical leads which pass through the shaft center from the clutch field coil. A horse shoe shaped brush retainer rides on each slip ring and is prevented from rotating by a quick release hook member which fits over a securing bar and is held in place by a spring member that also supplies the elec trical power to the brushes.

12 Claims, 4 Drawing Figures Sheet 1 of2 US. Patent Dec. 16, 1975 US. Patent Dec. 16,1975 Sheet20f2 3,926,132

YARN FEED ROLLER ASSEMBLY BACKGROUND OF THE INVENTION This invention relates to textile machinery, such as tufting machines and the like, and is particularly directed to yarn feed roll pattern attachments therefor.

Wide use is being made of pattern attachments for producing variations in pile height in pile fabric such as carpeting. A pattern attachment of this type is disclosed in US. Pat. of Hammel, No. 3,103,187. An improvement over the pattern attachment disclosed in the aforesaid patent is disclosed in U.S. Pat. of Singleton, No. 3,489,326, which discloses an arrangement in which two or more drive shafts rotating continuously at different speeds each have yarn feed rolls relatively rotatably mounted thereon. The rolls of the shafts are drivingly connected one to the other and include an electromagnetic clutch mounted within each roll for drivingly transmitting the rotational motion of the shaft to the respective roll. This allows the rolls to be driven selectively at the speed of one or the other drive shafts. The amount of yarn supplied to the needles of a tufting machine or the like is determined by the rotational speed of the feed rolls on which the yarn strand is wound, so that with a fixed needle stroke the amount of yarn supplied to the needle determines the pile height of the pile fabric produced. To create patterned pile effects the amount of yarn fed to the individual needles may be varied by driving the feed rolls selectively at different speeds, i.e., the speed of one or the other drive shafts.

In the pattern attachment disclosed in the aforesaid Singleton patent, the electromagnetic clutches which drivingly transmit the rotation of the shafts to the rolls includes a field coil mounted in a stationary clutch body, a clutch element keyed to rotate with the shaft and an axially movable armature member splined on the roll. A bearing member is necessarily located between the stationary field clutch body and the rotating clutch element. Since, in many cases, maintenance and replacement is occassioned by worn bearing elements, it is desirable to eliminate the aforementioned bearing members. Another member which it is desirable to eliminate is the retaining element or the like which is required to locate the stationary field member axially relative to the rotating clutch element. Moreover, since the prior art field member must be stationary, each of the members must be fixed to a bracket on the frame of the machine. A typical attachment for a tufting machine has 120 or more feed rolls so that assembly of the attachment can be quite time consuming. Furthermore, in the prior art attachment the electrical lead wires which supply electricity to the fixed field must pass out of the clutch body at each of the rolls, thus creating the possibility of the yarns snarling on the wires in the limited available space for the attachment.

Another problem presented by the prior art attachment is that machine down time may be excessive when changing from an operation where less needles and hence yarn ends are needed than the tufting machine needle bar is set up for and can accommodate. Examples of this occur when changing from full width products to partial width products and back again to full width, and also when tufting at a larger gauge than the needle bar is set for. In such cases the surplus yarn ends must be taken off the feed rolls. In the attachment illustrated in the aforestated I-Iammel patent this was accomplished by taking the yarns off the feed rolls and slipping them out between adjacent units and placing them on the stationary supporting bracket members between the rolls. However, in the improved attachment illustrated in the aforesaid Singleton patent, each drive shaft extends through all the associated feed rolls so the surplus yarn could not be slipped out from between adjacent rolls to place them on a stationary member. This necessitates the breaking of the yarn to remove them from the rolls. When changing back to produce full width or full gauge fabrics, the yarn then has to be completely rethreaded onto the roll and into the associated tube banks before being threaded into the yarn guides and needles.

SUMMARY OF THE INVENTION The present invention overcomes these deficiencies of the prior attachments by providing for each roll an electromagnetic clutch having its field element fixed for rotation on the associated drive shaft thereby eliminating the bearing and retaining members and, by com bining the functions of the field housing and the rotating clutch element into one unit, providing a roller of a greatly decreased width. The drive shafts are hollow and the electrical lead wires, which rotate with the field, are brought into the center of the shaft and extend axially to one end at which is located a slip ring assembly, one for each clutch on the shaft. A brush supporting assembly including support members are slidably received on the slip rings and are restrained against rotation by means of holding members adapted to embrace a securing bar. Electricity conducting spring fingers receive power from a selective source and communicate it to a conducting strip on the holding members and also function to bias the holding members against the securing bar. The brushes are received within metal containers threaded into the support members in contact with the conducting strips and receive electricity therefrom. The arrangement is such that it is a simple procedure to remove a single brush container and replace the associated brush. The holding member may also be removed readily at any slip ring for inspection or for cleaning the slip ring. Another feature of the invention is the provision of yarn holding gears having an incomplete periphery of gear teeth mounted on each shaft between pairs of rolls. The teeth of corresponding gears on the drive shafts mesh, thereby causing the gears to rotate until coming into contact with the no-teeth portion, whereupon the gears seize and remain stationary. Surplus yarn is placed on the holding gears and thereby maintained stationary when less than all of the needles in the tufting machine needle bar are required for the pile fabric being manufactured.

Accordingly, it is a primary object of the present invention to provide an improved yarn feed roller assembly which in comparison to the prior art assemblies is smaller, more easily manufactured and assembled, and which is more readily serviced when maintenance is required.

It is another object of this invention to' provide a yarn feed roller assembly having a plurality of feed rolls on each drive shaft and which includes a yarn holding member for maintaining surplus yarns stationary when manufacturing pile fabric using less than all the needles of the full machine.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects and advantages of the invention will be best understood upon reading the following detailed description of the invention with the accompanying drawings, in which:

FIG. 1 is a fragmentary sectional view through a yarn feed roller assembly constructed in accordance with the present invention for a tufting machine capable of producing three pile height patterned fabrics;

FIG. 2 is a fragmentary sectional view of one module of the yarn feed roller assembly taken substantially along line 2-2 of FIG. 1;

FIG. 3 is a cross sectional view taken substantially along line 3-3 of FIG. 2 illustrating one set of yarn holding gears; and

FIG. 4 is a fragmentary perspective view of the slip ring portion of the module shown in FIG. 2 illustrating the manner in which the brush supporting members may be removed from the assembly.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing there is illustrated in FIG. 1 a portion of a tuftin g machine frame supporting a feed roll assembly comprising spaced parallel modules having hollow drive shafts 11, 12 and 13. The shafts are rotatably mounted on brackets (not shown) secured to the frame 10 in a manner illustrated in the aforesaid Singleton patent. Each of the drive shafts is driven at a different speed in any conventional manner, for example, chains and sprockets as described in said Singleton patent. Preferably, the shaft 11 is driven at a low speed, shaft 13 at a high speed and shaft 12 at an intermediate speed. Rotatably mounted on each drive shaft is a plurality of respective feed roll units 15, 16 and 17. Since the units are all of the same construction only one of the units 16 on the intermediate speed shaft 12 will be described. It being understood that all of the roller units 16 preferably are alike, and that all of the units and 17 preferably are like the units 16.

Each roller unit 16 comprises a pair of feed rolls 18 and 18 of like construction but mounted back-to-back on the drive shaft. Feed roll 18 will therefore be described and a prime will indicate, when necessary, the corresponding element in rolls 18. The rolls, which preferably are constructed from a plastic material, each comprise a cylindrical sleeve 20. At the end thereof most remote from the feed roll 18', the sleeve 20 has an internal hub 22 mounted on and freely rotatable on the shaft 12. Gear teeth 24 are provided at a flanged outer periphery of the sleeve at the same end as the hub 22. The teeth of one roll mesh with those of the corresponding rolls on the other shaft 11 and 13 thereby to effect a driving coupling between such corresponding rolls. Each roll has a yarn carrying friction surface 26, such as rubber or the like, located on the periphery of the sleeve. Yarn 28 threaded from a tensioning device 30 and through a guide 32 are wound about the surfaces 26 of corresponding rolls. From the rolls, the yarn is fed a tube bank (not illustrated) and then to the needles at a rate determined by the speed of the particular shaft 11, 12 or 13 which at that time is drivingly coupled to those corresponding rolls. Located in the annular space between the sleeve 20 and the shaft 12 is an electromagnetic clutch having a clutch housing 34 keyed to the shaft 12 and an annular armature member 36 splined to the hub 22 and movable axially thereof into and out of operative engagement with the clutch housing upon actuation of the clutch. A field coil 38 is mounted within an annular slot 40 in the clutch housing. Actuation of the appropriate clutch couples the selected roll directly to its drive shaft 11, 12 or 13. The corresponding rolls on the other of said shafts are by means of the gear teeth thereby driven at the same speed as the selected roll. Thus, the speed of any of the shafts may be imparted to any of the rolls by actuating one of the electromagnetic clutches of the meshing corresponding rolls.

An electrical lead 42 extends from each clutch field coil 38 to an insulated electrical connector 44 mounted in the clutch housing and which is received in an electrical socket 46 mounted radially in the shaft and extending into the interior 48 of the shaft. Electrically connected to each socket 46 is an insulated electrical lead wire 50 which passes axially along the interior of the shaft to a slip ring assembly 52 mounted at one end of shaft preferably spaced from the rolls by, for example, a collar 54.

The slip ring assembly 52 comprises a plurality of slip rings 56, there being one slip ring for each roller clutch mounted on the shaft. The slip rings are mounted on the shaft by means of insulated collars 58 preferably one for each slip ring, keyed to the shaft. The slip rings are positioned on the collar and may be axially aligned by a shoulder 60 formed on the collar. The lead wires 50 are brought through a radial hole 62 formed in the collar and are secured by, for example, a solder joint 64 to a respective slip ring. There may be an extra slip ring mounted on the shaft to act as a common return for all the clutches, but preferably, since the voltage demands of the clutch are small, each coil 38 may be returned as at 66 to the clutch housing which is returned through the shaft to ground through the tufting machine frame. Conventional electrical conducting graphite brushes 68 supply electricity to the slip rings to energize the clutch coils.

To supply electrical power to the brushes 68 from a selective source such as a pattern control illustrated diagrammatically as 70 in FIG. 2, this invention provides a novel brush supporting assembly designated generally as 72 and best understood with reference to FIG. 4. The brush supporting assembly includes substantially U-shaped brush holding members 74, preferably one for each slip ring. Each of the members 74 is constructed of an insulated material, preferably a plastic or nylon, and includes a recess or grooved track 76 formed on the entire interior periphery of the member and having a width substantially equal to the width of the slip ring. The legs 78 and 80 of the members 74 are spaced one from the other such that the spacing between the base of the track 76 in the legs is substantially equal to the outer diameter of the slip rings, as is the diameter of the circular portion 82 of the members 74 at the base of the track. Consequently, the design is such that each brush holding member 74 is slidably fitted about a respective slip ring and bears thereon.

The outer periphery of the brush holding members 74 includes a recess 84 and an adjacent upstanding lug 86. Mounted in the recess 84 is a strip of conducting material 88, preferably brass, having an upstanding arm extending up the adjacent wall of the lug and bent to form a tab 92 overlying a portion of the outer peripheral surface thereof. Preferably each brush holding member 74 carries two brushes 68, one being redundant for safety, mounted at 60 to one another. Thus,

the recess 84 is formed with two surfaces at 60 to one another and the strip 88 is bent to form two more tabs 94 and 96 abutting these surfaces. The brushes are mounted in open ended cylindrical metal containers 98 each having a threaded portion of reduced diameter 100 at the bottom thereof, and a screw driver receiving slot 102 at the top thereof. The threaded portion 100 pass through holes formed in the tabs 92 and 94 and are threadedlyreceived in holes 104 tapped into the members 74 in such a manner that the body of the containers 98 contact the respective tab 94 or 96 to receive electricity therefrom as hereinafter described. The brushes 68 are inserted into the containers 98 and have a metal cap 106 of substantially the same diameter as the inner diameter of the container pressed onto the top end of the brush so that the cap 106 may conduct the electricity from the container to the brush or the brush may contact the container and receive current thereby. A spring 108 and a grub screw 110 are respectively positioned in the container after the brush to hold the unit together. Consequently, any electrical current received by the strip 83 is communicated to the brush.

In order to restrain the U-shaped members 74 from rotating with the slip rings there is provided a novel arrangement including a radial slot 1 1 1 forming a hook in the lug 86. Supplied on the frame of the tufting machine is a bracket 112 having a plurality ofapertured arms 114, preferably one corresponding to each slip ring. A bar 116 extends through the apertures in each of the arms 114 and is vertically secured thereby so as to be adapted to be embraced by the slots 111. When installed, the members 74 slide over the slip rings until the track 76 at the portion 82 bears on the slip ring, and the member is then pivoted until the slot 111 embraces the bar 116. It is urged against the bar by means of curved spring fingers 118 of sufficient strength to overcome the rotational forces of the slip rings. The springs 118 act against the tabs 92 to urge the lugs 86 against the bar 116. In so doing they also conduct electrical current to the tabs 92 from insulated wires 120 leading from the pattern control. The springs are mounted on the bracket 112 preferably through the medium of an insulating strip member 122. The wires include conventional connectors 124 which receive connecting portions 126 formed on the ends of the spring members.

This brush and slip ring arrangement has been designed with maintenance considerations foremost in mind. With this design it is possible to remove a single brush container by unscrewing the container to replace the brush inside. However, as illustrated, the containers 98 are shorter than the distance between the shaft centerline and the slot 111 so that removal of the brush in this manner is not necessary, since it is also possible to remove the entire brush holder 74 at any slip ring and have access to the slip rings for cleaning purposes and to remove the brushes. Hence, the only time the clutch module need be removed is if clutch coil failure occurs or if it is necessary to replace worn out clutch housings.

Another aspect of this invention is the provision of a yarn holding gear 128, best illustrated in FIGS. 2 and 3. The yarn holding gear comprises a disc member having a central opening 130 adapted to be assembled on central axially extending hub portions 132 of the clutch field members 34. Preferably each feed roll unit 16 has a gear 128 positioned between each of the feed rolls 18 and 18 and which is mounted on the hubs 132 and 132 of the respective field members 34 and 34. The

gear includes an annular groove 134 and 136 on each face thereof which is entrapped between facing portions of the sleeves 20 and 20. The gear thus may rotate by the frictional mounting when the rolls l8 and 18 are rotated and become stationary by means now to be described.

Each gear 128 includes peripheral circumferential grooves 138 and 140 for receiving surplus yarn when manufacturing pile fabric using less than all the needles which the tufting machine is capable of utilizing, as heretofore described. There is a yarn holding gear on each of the shafts 11 and 13 corresponding to each gear 128 on the shaft 12. Each gear has teeth 142 out in only a small portion of the gears outermost periphery. Only the gear 128 on the intermediate speed shaft 12 need have teeth on two portions where it meshes with the gears on the other shafts, however, for ease of manufacture and logistics, each gear will be the same as the gear 128. The outer diameter of each gear is equal to the addendum diameter or outer tip diameter of the teeth so that the gears will bind or seize upon rotating to the noteeth portions. This locks the gears stationary since the direction of rotation is never reversed. The gears are, of course, assembled so that the teeth initially mesh and upon the first rotation of the rolls 18 and 18' the gears become stationary so that surplus yarn 144 may be placed in the grooves 138 and 140 and held stationary during certain production runs.

Numerous alterations of the structure herein disclosed will suggest themselves to those skilled in the art. For example, rather than a three pile height pattern attachment which is the preferred embodiment, a two pile height attachment may be used which has only two corresponding roll modules rather than the three illustrated. However, it is to be understood that the present disclosure relates to a preferred embodiment of the invention which is for purposes of illustration only and not to be construed as a limitation of the invention. All such modifications which do not depart from the spirit of the invention are intended to be included within the scope of the appended claims.

Having thus set forth the nature of the invention, what is claimed herein is:

1. A yarn feed roller assembly for a tufting machine including a plurality of hollow drive shafts, at least a feed roll on each of said shafts and rotatable relative thereto, the corresponding rolls of the said shafts being drivingly connected one to another, an electromagnetic clutch means between each roll and its respective shaft comprising a first element fixed for rotation with said shaft and a second element axially movable relative to said shaft, said feed roll being rotationally fixed to said axially movable member, a slip ring for each roll, means on each shaft for mounting a slip ring corresponding to each roll on said shaft, electrical conducting means connected to said first element and extending through said shaft axially into operative electrical contact with a corresponding slip ring, electricity conducting brushes, brush supporting means held against rotation and positioned on said slip rings for retaining at least one brush in contact with each slip ring and for communicating electricity from a source selectively to the brushes, whereby the electromagnetic clutches may be actuated to drivingly couple the rolls to one or the other of the drive shafts.

2. A yarn feed roller assembly as recited in claim 1 wherein said brush supporting means comprise a substantially U-shape member slidably fitted about the slip rings and bearing thereon, and holding means for restraining said U-shape members from rotating with the slip rings.

3. A yarn feed roller assembly as recited in claim 2 wherein said holding means includes a bar secured to said machine, a lug on said U-shape members having means adapted to embrace said bar, and biasing means for urging said lug against said bar.

4. A yarn feed roller assembly as recited in claim 2 wherein said U-shape members include recessed tracks for slidably receiving said slip rings.

5. A yarn feed roller assembly as recited in claim 2 wherein said brush supporting means includes electricity conducting brush containers threaded into said U- shape members, one brush being received in each container, means for conducting electricity from the source to said containers, and means for conducting electricity from said containers to the respective brush.

6. A yarn feed roller assembly as recited in claim 3 wherein said brush supporting means includes an electricity conducting element on the U-shape members and having an arm disposed on said lug, said biasing means comprising an electricity conducting spring finger engaging said arm, means for conducting electricity from the source to the finger, electricity conducting brush containers threadedly received in said U-shape members and contacting said conducting elements, a brush mounted in each container, and means for conducting electricity from said containers to the respective brush.

7. A yarn feed roller assembly as recited in claim 2 comprising a plurality of feed rolls on each shaft and an individual U-shape member for each slip ring.

8. A yarn feed roller assembly as recited in claim 7 wherein all the slip rings on each shaft are axially disposed adjacent one end of said shaft, and means including an insulating collar for mounting said slip rings on the shaft and for spacing said slip rings one from the other.

9. A yarn feed roller assembly as recited in claim 7 wherein said holding means comprises a bar for each shaft secured to said machine, a lug having slotted means formed on said U-shape members for embracing a respective bar, an electricity conducting element on each U-shape member having an arm disposed on said lug, an electricity conducting spring finger contacting each arm for conducting electricity to the arm and for urging the lug against said bar, means for conducting electricity from the source to each finger, at least one electricity conducting brush container threadedly received in each U-shape member and contacting the conducting element, a brush mounted in each container, and means for conducting electricity from said container to the brush.

10. A yarn feed roller assembly as recited in claim 1 comprising a plurality of feed rolls on each shaft, a stationary yarn holding member disposed between pairs of rolls for receiving selected yarns from the adjacent rolls and for holding said yarns stationary.

11. A yarn feed roller assembly as recited in claim 10 wherein said yarn holding member comprises a segmented gear supported on each of said shafts, each gear having an incomplete periphery of gear teeth, the corresponding gears of the shafts being disposed so that the teeth are adapted to intermesh one to the other and the no-teeth portions are adapted to contact one another, and means for applying a rotational force to the gears whereby said gears will seize upon disengagement of the teeth.

12 A yarn feed roller assembly as recited in claim 11 wherein each feed roll comprises a cylindrical sleeve, each of said gears being mounted on the first elements of the pair of rolls engaging facing ends of the sleeves. 

1. A yarn feed roller assembly for a tufting machine including a plurality of hollow drive shafts, at least a feed roll on each of said shafts and rotatable relative thereto, the corresponding rolls of the said shafts being drivingly connected one to another, an electromagnetic clutch means between each roll and its respective shaft comprising a first element fixed for rotation with said shaft and a second element axially movable relative to said shaft, said feed roll being rotationally fixed to said axially movable member, a slip ring for each roll, means on each shaft for mounting a slip ring corresponding to each roll on said shaft, electrical conducting means connected to said first element and extending through said shaft axially into operative electrical contact with a corresponding slip ring, electricity conducting brushes, brush supporting means held against rotation and positioned on said slip rings for retaining at least one brush in contact with each slip ring and for communicating electricity from a source selectively to the brushes, whereby the electromagnetic clutches may be actuated to drivingly couple the rolls to one or the other of the drive shafts.
 2. A yarn feed roller assembly as recited in claim 1 wherein said brush supporting means comprise a substantially U-shape member slidably fitted about the slip rings and bearing thereon, and holding means for restraining said U-shape members from rotating with the slip rings.
 3. A yarn feed roller assembly as recited in claim 2 wherein said holding means includes a bar secured to said machine, a lug on said U-shape members having means adapted to embrace said bar, and biasing means for urging said lug against said bar.
 4. A yarn feed roller assembly as recited in claim 2 wherein said U-shape members include recessed tracks for slidably receiving said slip rings.
 5. A yarn feed roller assembly as recited in claim 2 wherein said brush supporting means includes electricity conducting brush containers threaded into said U-shape members, one brush being received in each container, means for conducting electricity from the source to said containers, and means for conducting electricity from said containers to the respective brush.
 6. A yarn feed roller assembly as recited in claim 3 wherein said brush supporting means includes an electricity conducting element on the U-shape members and having an arm disposed on said lug, said biasing means comprising an electricity conducting spring finger engaging said arm, means for conducting electricity from the source to the finger, electricity conducting brush containers threadedly received in said U-shape members and contacting said conducting elements, a brush mounted in each container, and means for conducting electricity from said containers to the respective brush.
 7. A yarn feed roller assembly as recited in claim 2 comprising a plurality of feed rolls on each shaft and an individual U-shape member for each slip ring.
 8. A yarn feed roller assembly as recited in claim 7 wherein all the slip rings on each shaft are axially disposed adjacent one end of said shaft, and means including an insulating collar for mounting said slip rings on the shaft and for spacing said slip rings one from the other.
 9. A yarn feed roller assembly as recited in claim 7 wherein said holding means comprises a bar for each shaft secured to said machine, a lug having slotted means formed on said U-shape members for embracing a respective bar, an electricity conducting element on each U-shape member having an arm disposed on said lug, an electricity conducting spring finger contacting each arm for conducting electricity to the arm and for urging the lug against said bar, means for conducting electricity from the source to each finger, at least one electricity conducting brush container threadedly received in each U-shape member and contacting the conducting element, a brush mounted in each container, and means for conducting electricity from said container to the brush.
 10. A yarn feed roller assembly as recited in claim 1 comprising a plurality of feed rolls on each shaft, a stationary yarn holding member disposed between pairs of rolls for receiving selected yarns from the adjacent rolls and for holding said yarns stationary.
 11. A yarn feed roller assembly as recited in claim 10 wherein said yarn holding member comprises a segmented gear supported on each of said shafts, each gear having an incomplete periphery of gear teeth, the corresponding gears of the shafts being disposed so that the teeth are adapted to intermesh one to the other and the no-teeth portions are adapted to contact one another, and means for applying a rotational force to the gears whereby said gears will seize upon disengagement of the teeth.
 12. A yarn feed roller assembly as recited in claim 11 wherein each feed roll comprises a cylindrical sleeve, each of said gears being mounted on the first elements of the pair of rolls engaging facing ends of the sleeves. 